Re: different rules
That's basically kicking the victim in the shins once more.
It's also sparing "the victim" and the company from what would otherwise be an inevitable trial at which facts would be established and proven, or they wouldn't. If you want to sack someone on another persons say so, you're going to need evidence to back that up, which given the nature of the cases under discussion, may be very difficult to obtain. Presumably if there was sufficient evidence, the perpetrator would have been arrested, tried, and found guilty; dismissal without recompense them becomes easy to achieve.
Where there really isn't any objective evidence, just two parties with differing verions of events, the avoidance of a trial is less bad PR for the company, less traumatic for the accuser, and produces a defined outcome that all parties can live with. It's also a lot cheaper in terms of lawyers - tens or hundreds of millions at stake will tend to produce legal teams at the higher end of the billing spectrum.